A quality-control crackdown at Foxconn is causing the iPhone 5 to be in short supply. Apparently Foxconn wants to cut the number of devices shipped with nicks and scratches.

The problem is caused by Apple's decision to use a type of aluminium that helps make the smartphone thinner and lighter. The problem is that it scratches more often than a dog with mange and lots of the problems are caused at the plant. Senior Apple managers told executives at Foxconn near the end of September to tighten production standards.

Stricter benchmarks have hampered production of the iPhone 5's anodized aluminium housings, forcing Foxconn to idle factories, or at least send its workers back to school. The slowdown is heightening supply concerns that the Tame Apple Press claims cost Apple about $60 billion in market value since the iPhone debut.

While Apple sold 5 million iPhone 5s the first weekend the device was on sale, the Tame Apple Press claim the figure would have been higher if not for supply constraints. The fact that the phone is not as popular as others because important functions are broken has not been facted into the equation yet.

But analysts at RBC Capital Markets have cut their forecast for iPhone 5 sales for the December quarter, partly due to a dearth of components. They project sales of 49 million units, compared with 57 million.